The Nazca plate or Nasca plate, named after the Nazca region of southern

Peru Peru, officially the Republic of Peru, is a country in western South America. It is bordered in the north by Ecuador and Colombia, in the east by Brazil, in the southeast by Bolivia, in the south by Chile, and in the south and west by the Pac ...

, is an oceanic

tectonic plate Plate tectonics (, ) is the scientific theory that the Earth's lithosphere comprises a number of large tectonic plates, which have been slowly moving since 3–4 billion years ago. The model builds on the concept of , an idea developed durin ...

in the eastern

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five Borders of the oceans, oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is ...

basin off the west coast of

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

. The ongoing subduction, along the Peru–Chile Trench, of the Nazca plate under the

South American plate The South American plate is a major tectonic plate which includes the continent of South America as well as a sizable region of the Atlantic Ocean seabed extending eastward to the African plate, with which it forms the southern part of the Mid ...

is largely responsible for the Andean

orogeny Orogeny () is a mountain-mountain formation, building process that takes place at a convergent boundary, convergent plate margin when plate motion compresses the margin. An or develops as the compressed plate crumples and is tectonic uplift, u ...

. The Nazca plate is bounded on the west by the Pacific plate and to the south by the Antarctic plate through the East Pacific Rise and the Chile Rise, respectively. The movement of the Nazca plate over several hotspots has created some volcanic islands as well as east–west running seamount chains that subduct under

. Nazca is a relatively young plate in terms of the age of its rocks and its existence as an independent plate, having been formed from the breakup of the Farallon plate about 23 million years ago. The oldest rocks of the plate are about 50 million years old.

Boundaries

East Pacific and Chile Rise

A triple junction, the Chile triple junction, occurs on the seafloor of the

off Taitao and Tres Montes Peninsula at the southern coast of

Chile Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes, Andes Mountains and the Paci ...

. Here, three

tectonic Tectonics ( via Latin ) are the processes that result in the structure and properties of the Earth's crust and its evolution through time. The field of ''planetary tectonics'' extends the concept to other planets and moons. These processes ...

plates meet: the Nazca plate, the

, and the Antarctic plate.

Peru–Chile Trench

The eastern margin is a

convergent boundary A convergent boundary (also known as a destructive boundary) is an area on Earth where two or more lithospheric plates collide. One plate eventually slides beneath the other, a process known as subduction. The subduction zone can be defined by a ...

subduction zone under the South American plate and the

Andes Mountains The Andes ( ), Andes Mountains or Andean Mountain Range (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long and wide (widest between 18°S ...

, forming the Peru–Chile Trench. The southern side is a

divergent boundary In plate tectonics, a divergent boundary or divergent plate boundary (also known as a constructive boundary or an extensional boundary) is a linear feature that exists between two List of tectonic plates, tectonic plates that are moving away fr ...

with the Antarctic plate, the Chile Rise, where seafloor spreading permits

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma (sometimes colloquially but incorrectly referred to as ''lava'') is found beneath the surface of the Earth, and evidence of magmatism has also ...

to rise. The western side is a divergent boundary with the Pacific plate, forming the East Pacific Rise. The northern side is a divergent boundary with the Cocos plate, the Cocos–Nazca spreading centre. The subduction of the Nazca plate under southern Chile has a history of producing massive

earthquake An earthquakealso called a quake, tremor, or tembloris the shaking of the Earth's surface resulting from a sudden release of energy in the lithosphere that creates seismic waves. Earthquakes can range in intensity, from those so weak they ...

s, including the largest ever recorded on earth, the moment magnitude 9.5 1960 Valdivia earthquake.

Intraplate features

Hotspots

A second triple junction occurs at the northwest corner of the plate where the Nazca, Cocos, and Pacific plates all join off the coast of

Colombia Colombia, officially the Republic of Colombia, is a country primarily located in South America with Insular region of Colombia, insular regions in North America. The Colombian mainland is bordered by the Caribbean Sea to the north, Venezuel ...

. Yet another triple junction occurs at the southwest corner at the intersection of the Nazca, Pacific, and Antarctic plates off the coast of southern

. At each of these triple junctions an '' anomalous'' microplate exists, the Galapagos microplate at the northern junction and the Juan Fernandez microplate at the southern junction. The Easter Island microplate is a third microplate that is located just north of the Juan Fernandez Microplate and lies just west of Easter Island.

Aseismic ridges

The Carnegie Ridge is a and up to feature on the ocean floor of the northern Nazca plate that includes the Galápagos archipelago at its western end. It is being subducted under South America with the rest of the Nazca plate.

Plate motion

The absolute motion of the Nazca plate has been calibrated at east motion (88°), one of the fastest absolute motions of any tectonic plate. The subducting Nazca plate, which exhibits unusual flat slab subduction, is tearing as well as deforming as it is subducted (Barzangi and Isacks). The subduction has formed and continues to form the volcanic

Andes The Andes ( ), Andes Mountains or Andean Mountain Range (; ) are the List of longest mountain chains on Earth, longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range ...

Mountain Range. Deformation of the Nazca plate even affects the

geography Geography (from Ancient Greek ; combining 'Earth' and 'write', literally 'Earth writing') is the study of the lands, features, inhabitants, and phenomena of Earth. Geography is an all-encompassing discipline that seeks an understanding o ...

Bolivia Bolivia, officially the Plurinational State of Bolivia, is a landlocked country located in central South America. The country features diverse geography, including vast Amazonian plains, tropical lowlands, mountains, the Gran Chaco Province, w ...

, far to the east (Tinker et al.). The 1994 Bolivia earthquake occurred on the Nazca plate; this had a magnitude of 8.2

M_w

, which at that time was the strongest instrumentally recorded earthquake occurring deeper than . Aside from the

Juan Fernández Islands The Juan Fernández Islands () are a sparsely inhabited series of islands in the South Pacific Ocean, reliant on tourism and fishing. Situated off the coast of Chile, they are composed of three main volcanic islands: Robinson Crusoe Island, R ...

, this area has very few other islands that are affected by the earthquakes resulting from complicated movements at these junctions.

Geologic history

The precursor of the Nazca plate, Juan de Fuca plate, and the Cocos plate was the Farallon plate, which split in the late

Oligocene The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...

, about 22.8 Mya, a date arrived at by interpreting magnetic anomalies. Subduction under the South American continent began about 140 Mya, although the formation of the high parts of the Central Andes and the Bolivian orocline did not occur until 45 Mya. It has been suggested that the mountains were forced up by the subduction of the older and heavier parts of the plate, which sank more quickly into the mantle.

References

Bibliography

Extreme Science site: "A Lesson in Plate Tectonics"
The basics explained.

* Muawia Barazangi and Bryan L. Isacks, "Spatial distribution of earthquakes and subduction of the Nazca plate beneath South America" in ''Geology'' Vol. 4, No. 11, pp. 686–692
Abstract
*Mark Andrew Tinker, Terry C. Wallace, Susan L. Beck, Stephen Myers, and Andrew Papanikolas, "Geometry and state of stress of the Nazca plate beneath Bolivia and its implication for the evolution of the Bolivian orocline" in ''Geology'' 24(5), pp. 387–39
Abstract
* Cahill, T. and B. Isacks (1992). "Seismicity and shape of the subducted Nazca plate." ''Journal Geophysical Research'' 97 (12) * James, D. (1978). "Subduction of the Nazca plate beneath Central Peru." ''Geology'' 6 (3) pp 174–178
Martin Meschede and Udo Barckhausen, "Plate tectonic evolution of the Cocos-Nazca spreading center"
{{Coord, 15, S, 85, W, region:PE_type:country, display=title Tectonic plates Geology of Chile Natural history of Oceania Natural history of South America Geology of the Pacific Ocean